This invention relates to sails, and more particularly to the forming of an air envelope in a sail and the shaped parts for the contouring of sails.
In the building of sailboats, much effort is devoted to improving the contour of the sails and reducing the resistance or wind drag of the rigging. A well known prerequisite of sailboats is that the craft must utilize the atmospheric wind from two sides.
The use of a contour mast with a mast contour that extends sternward beyond the usual streamline form of the fixed mast is a well known approach to improving the contour of the sail and enabling the craft to utilize atmospheric wind from two sides. The contour mast generally has a rotatable arrangement and can be run with a semirigid sail or with a lath sail as described in Segler Lexikon published by Joachim Schult Verlag Klasing and Co. GmbH, Bielefeld 1978, Second Edition, page 311. In many instances the rigid sail parts have a streamlined form with concave and nonvariable arches on both sides. Rigid sails, however, have not been widely accepted because they cannot be given a slight but often critical twist which at any level above the water gives the sail the correct angle of incidence that corresponds to the wind gradient of the atmospheric wind at an increasing level of the surface of the water (cf. The Sail-Jeremy Howard-Williams, German edition published by Klasing and Co., Bielfeld and Berlin 1969).
Other known sail arrangements such as the rigging for a sail plank or surfboard with a sail as disclosed in German Pat. No. 1,914,604 and a wind propelled vehicle as disclosed in Australian Pat. No. 46552/79 relate to the attachment of the mast on a sail plank or surfboard as well as the connection between the mast and two outwardly curved main booms. The German Pat. No. 1,914,604 further teaches that the fore leech of a sail for a sail plank or surfboard can be formed as a hem into which the mast is introduced. However, it has been found that no fundamental improvement in the contour of the sail is achieved as long as the mast remains the edge of wind attack of the main sail.
It is thus desirable to provide a sail which is not dependent on the mast to form the edge of wind attack of the main sail.